Internal combustion engine with common rail injection

ABSTRACT

An internal combustion engine includes first and second common rails each having a metering or pressure regulating valve, with the valves settable at different pressure values from one another. Rotors are each sealingly and rotationally received within a respective cavity to define at least one combustion chamber of variable volume. The engine includes first and second fuel injectors for each of the rotors. Each first fuel injector is in fluid communication with the first common rail and each second fuel injector is in fluid communication with the second common rail. A method of feeding fuel in an internal combustion engine is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/707,000 filed Sep. 18, 2017, which is a continuation of U.S.application Ser. No. 14/926,357 filed Oct. 29, 2015, which is acontinuation of U.S. application Ser. No. 13/796,239 filed Mar. 12,2013, the entire contents of all of which are incorporated by referenceherein.

TECHNICAL FIELD

The application relates generally to internal combustion engines and,more particularly, to fuel injection in such engines.

BACKGROUND OF THE ART

Some reciprocating internal combustion engines have a main and pilotfuel injection performed by a same fuel injector. The fuel injectors maybe fed by a common rail, where for example each injector includes apressure intensification mechanism to perform the main injection at anincreased pressure and performs a pilot injection using the common railpressure. Accordingly, a relatively complex configuration may berequired for each injector.

Some internal combustion engines, including some rotary engines, includea pilot subchamber for pilot ignition. However, known arrangements arenot optimized, in terms of combustion arrangements and characteristics,and thus room for improvement exists.

SUMMARY

In one aspect, there is provided an internal combustion enginecomprising: an outer body defining an internal cavity; a rotatable bodysealingly and rotationally received within the internal cavity to defineat least one combustion chamber of variable volume; a pilot subchamberdefined in the outer body in communication with the internal cavity; apilot fuel injector having a tip in communication with the pilotsubchamber; an ignition element positioned to ignite fuel within thepilot subchamber; a main fuel injector spaced apart from the pilot fuelinjector and having a tip in communication with the internal cavity at alocation spaced apart from the pilot subchamber; a common rail in fluidcommunication with the main fuel injector and with the pilot fuelinjector; and a pressure regulating mechanism in fluid communicationwith the common rail for regulating a fuel pressure therein.

In another aspect, there is provided a rotary internal combustion enginecomprising: an outer body having an internal cavity defined by twoaxially spaced apart end walls and a peripheral wall extending betweenthe end walls; a rotor body rotatable within the internal cavity insealing engagement with the peripheral and end walls and defining atleast one chamber of variable volume in the internal cavity around therotor body; a pilot subchamber defined in the outer body in fluidcommunication with the internal cavity; a pilot fuel injector having atip in communication with the pilot subchamber; an ignition elementpositioned to ignite fuel within the pilot subchamber; a main fuelinjector spaced apart from the pilot fuel injector, the main fuelinjector having a tip in communication with the internal cavity at alocation spaced apart from the pilot subchamber; a common rail in fluidcommunication with the main fuel injector and with the pilot fuelinjector; and a pressure regulating mechanism in fluid communicationwith the common rail for regulating a fuel pressure therein.

In a further aspect, there is provided a method of combusting fuel in aninternal combustion engine having a rotatable body defining at least onecombustion chamber, the method comprising: pressurizing the fuel in acommon rail; feeding a pilot injector with the common rail to injectfuel in a pilot subchamber; igniting the fuel within the pilotsubchamber; circulating the ignited fuel out of the pilot subchamber andinto one of the at least one combustion chamber; and feeding a maininjector separate from the pilot injector with the common rail to injectfuel into the one of at least one combustion chamber spaced apart fromthe pilot subchamber and the pilot injector.

In a further aspect, there is provided an internal combustion enginecomprising: an outer body defining an internal cavity; a moveable bodysealingly and moveably received within the internal cavity to define atleast one combustion chamber of variable volume; a pilot subchamberdefined in the outer body in communication with the internal cavity; apilot fuel injector having a tip in communication with the pilotsubchamber; an igniter positioned to ignite fuel within the pilotsubchamber; a main fuel injector spaced apart from the pilot fuelinjector and having a tip in communication with the internal cavity at alocation spaced apart from the pilot subchamber; and a common rail influid communication with the main fuel injector and with the pilot fuelinjector.

In a further aspect, there is provided an internal combustion enginecomprising: an outer body defining internal cavities; for each of theinternal cavities: a respective reciprocating piston sealingly andmoveably received within the internal cavity and defining a respectivecombustion chamber of variable volume therein, a respective pilotsubchamber defined in the outer body in fluid communication with theinternal cavity, a respective pilot fuel injector having a tip incommunication with the respective pilot subchamber, a respective igniterpositioned to ignite fuel within the respective pilot subchamber, and arespective main fuel injector spaced apart from the respective pilotfuel injector, the respective main fuel injector having a tip incommunication with the internal cavity at a location spaced apart fromthe respective pilot subchamber; and a common rail in fluidcommunication with each main fuel injector and with each pilot fuelinjector.

In a further aspect, there is provided a method of combusting fuel in aninternal combustion engine having a plurality of reciprocating pistonseach received in a respective internal cavity defining a respectivecombustion chamber of variable volume, the method comprising:pressurizing the fuel in a common rail; and for each respective internalcavity: feeding a respective pilot injector with the common rail toinject fuel in a respective pilot subchamber, igniting the fuel withinthe respective pilot subchamber, circulating the ignited fuel out of therespective pilot subchamber and into the respective combustion chamber,and feeding a respective main injector separate from the respectivepilot injector with the common rail to inject fuel into the respectivecombustion chamber spaced apart from the respective pilot subchamber andpilot injector.

In a further aspect, there is provided a rotary internal combustionengine comprising: a first common rail having a first metering orpressure regulating valve in fluid communication therewith; a secondcommon rail having a second metering or pressure regulating valve influid communication therewith, the first and second metering or pressureregulating valves being settable at different pressure values from oneanother; and at least two rotors each sealingly and rotationallyreceived within a respective cavity to define at least one combustionchamber of variable volume, the engine including, for each of therotors: a pilot subchamber in communication with the respective cavity,a pilot fuel injector in communication with the pilot subchamber, anignition element positioned to ignite fuel within the pilot subchamber,and a main fuel injector in communication with the respective cavity ata location spaced apart from the pilot subchamber; wherein each mainfuel injector is in fluid communication with the first common rail andeach pilot fuel injector is in fluid communication with the secondcommon rail.

In a further aspect, there is provided a rotary internal combustionengine comprising: a first common rail having a first metering orpressure regulating valve in fluid communication therewith; a secondcommon rail having a second metering or pressure regulating valve influid communication therewith, the first and second metering or pressureregulating valves being settable at different pressure values from oneanother; an outer body having at least two rotor cavities each definedby two axially spaced apart end walls and a peripheral wall extendingbetween the end walls; a rotor received in each of the at least tworotor cavities, each rotor being rotatable within the rotor cavity insealing engagement with the peripheral and end walls and defining atleast one chamber of variable volume in the rotor cavity; and for eachof the rotor cavities: a pilot subchamber defined in the outer body influid communication with the rotor cavity, a pilot fuel injector incommunication with the pilot subchamber, an ignition element positionedto ignite fuel within the pilot subchamber, and a main fuel injector incommunication with the rotor cavity at a location spaced apart from thepilot subchamber; wherein each main fuel injector is in fluidcommunication with the first common rail and each pilot fuel injector isin fluid communication with the second common rail.

In a further aspect, there is provided a method of combusting fuel in aninternal combustion engine having at least two rotors each defining atleast one combustion chamber, the method comprising: pressurizing thefuel in a first common rail at a first pressure; pressurizing the fuelin a second common rail separate from the first common rail at a secondpressure different from the first pressure; and for each of the rotorsof the engine: feeding a respective pilot injector with fuel at thesecond pressure from the second common rail to inject fuel in arespective pilot subchamber, igniting the fuel within the respectivepilot subchamber, circulating the ignited fuel out of the respectivepilot subchamber and into the one of the combustion chambers, andfeeding a respective main injector with fuel at the first pressure fromthe first common rail to inject fuel into the one of the combustionchambers spaced apart from the respective subchamber.

In a further aspect, there is provided a rotary internal combustionengine comprising: a first common rail having a first metering orpressure regulating valve in fluid communication therewith; a secondcommon rail having a second metering or pressure regulating valve influid communication therewith, the first and second metering or pressureregulating valves being settable at different pressure values from oneanother; and at least two rotors each sealingly and rotationallyreceived within a respective cavity to define at least one combustionchamber of variable volume; and for each of the rotors, a first fuelinjector in fluid communication with the first common rail and a secondfuel injector in fluid communication with the second common rail.

In a further aspect, there is provided a rotary internal combustionengine comprising: a first common rail having a first metering orpressure regulating valve in fluid communication therewith; a secondcommon rail having a second metering or pressure regulating valve influid communication therewith, the first and second metering or pressureregulating valves being settable at different pressure values from oneanother; an outer body having at least two rotor cavities each definedby two axially spaced apart end walls and a peripheral wall extendingbetween the end walls; a rotor received in each of the at least tworotor cavities, each rotor being rotatable within the rotor cavity insealing engagement with the peripheral and end walls and defining atleast one chamber of variable volume in the rotor cavity; for each ofthe rotor cavities, a first fuel injector in fluid communication withthe first common rail; and for each of the rotor cavities, a second fuelinjector in fluid communication with the second common rail.

In a further aspect, there is provided a method of feeding fuel in aninternal combustion engine having at least two rotors each defining atleast one combustion chamber, the method comprising: pressurizing thefuel in a first common rail at a first pressure; pressurizing the fuelin a second common rail separate from the first common rail at a secondpressure different from the first pressure; and for each of the rotorsof the engine: feeding a respective first injector with fuel at thefirst pressure from the first common rail; and feeding a respectivesecond injector with fuel at the second pressure from the second commonrail.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of a rotary internalcombustion engine in accordance with a particular embodiment;

FIG. 2 is a schematic view of an injection system which can be used withan internal combustion engine such as shown in FIG. 1, in accordancewith a particular embodiment;

FIG. 3 is a schematic view of an injection system which can be used withan internal combustion engine such as shown in FIG. 1, in accordancewith another particular embodiment; and

FIG. 4 is a schematic view of an injection system which can be used withan internal combustion engine such as shown in FIG. 1, in accordancewith a further particular embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, a rotary internal combustion engine 10 known as aWankel engine is schematically shown. In a particular embodiment, therotary engine 10 is used in a compound cycle engine system such asdescribed in Lents et al.'s U.S. Pat. No. 7,753,036 issued Jul. 13,2010, as described in Julien et al.'s U.S. Pat. No. 7,775,044 issuedAug. 17, 2010, or as described in U.S. patent application Ser. Nos.13/554,517 and 13/554,564 both filed Jul. 20, 2012, the entire contentsof all of which are incorporated by reference herein. The compound cycleengine system may be used as a prime mover engine, such as on anaircraft or other vehicle, or in any other suitable application. In anyevent, in such a system, air is compressed by a compressor beforeentering the Wankel engine, and the engine drives one or more turbine(s)of the compound engine. In another embodiment, the rotary engine 10 isused with a turbocharger without being compounded; in anotherembodiment, the rotary engine 10 is used without a turbocharger, withair at atmospheric pressure, as a stand-alone engine. In one embodiment,the rotary engine 10 may be applicable to land base systems including,but not limited to, generators.

The engine 10 is shown and described herein as a Wankel engine as anexample only. It is understood that the engine 10 may alternately be anyother adequate type of internal combustion engine having a pilotsubchamber for ignition, such as for example a reciprocating engine, ora rotary engine having a different configuration than that of a Wankelengine. For example, in a particular embodiment, the rotary engine maybe a single or eccentric type rotary engine in which the rotor rotatesabout a fixed center of rotation. For example, the rotary engine may bea sliding vane engine, such as described in U.S. Pat. No. 5,524,587issued Jun. 11, 1996 or in U.S. Pat. No. 5,522,356 issued Jun. 4, 1996,the entire contents of both of which are incorporated by referenceherein. In another particular embodiment, the rotary engine may be anoscillatory rotating engine, including two or more rotors rotating atdifferent angular velocities, causing the distance between portions ofthe rotors to vary and as such the chamber volume to change. In anotherparticular embodiment, the rotary engine may be a planetary rotatingengine having a different geometry than that of the Wankel engine, suchas for example a planetary engine having a rotor cavity with anepitrochoid profile defining three lobes and a rotor with four apexportions. Examples of such non-Wankel rotary engines are shown inApplicant's U.S. application Ser. No. 13/750,523 filed Jan. 25, 2013,the entire contents of which is incorporated by reference herein. Otherrotary engine geometries are also possible.

The engine 10 generally includes at least one moveable body received ina corresponding internal cavity of an outer body to define at least onecombustion chamber. For example, the engine 10 may be a reciprocatingengine with a plurality of internal cavities 20′ each receiving amoveable body in the form of a reciprocating piston 24′ (FIGS. 2-4). Theengine 10 may alternately be a rotary engine with a plurality ofinternal cavities 20 each receiving a moveable body on the form of arotatable body or rotor 24.

Referring back to FIG. 1, in the particular embodiment shown, the engine10 comprises an outer body 12 having at least one rotor cavity 20 (onlyone of which is shown) each defined by axially-spaced end walls 14 and aperipheral wall 18 extending therebetween, with a rotatable body orrotor 24 received in each cavity 20. The inner surface 19 of theperipheral wall 18 of each cavity 20 has a profile defining two lobes,which is preferably an epitrochoid.

In the case of a multiple rotor engine, the outer body 12 may beintegral or defined by a plurality of body portions each defining arespective one of the cavities 20 and receiving a respective one of therotors 24.

Each rotor 24 is received within the respective cavity 20, with thegeometrical axis of the rotor 24 being offset from and parallel to theaxis of the outer body 12. Each rotor 24 has axially spaced end faces 26adjacent to the outer body end walls 14, and a peripheral face 28extending therebetween. The peripheral face 28 defines threecircumferentially-spaced apex portions 30 and a generally triangularprofile with outwardly arched sides. The apex portions 30 are in sealingengagement with the inner surface of peripheral wall 18 to form threerotating working or combustion chambers 32 between the inner rotor 24and outer body 12. A recess (not shown) is defined in the peripheralface 28 of the rotor 24 between each pair of adjacent apex portions 30,to form part of the corresponding chamber 32.

The combustion chambers 32 are sealed. Each rotor apex portion 30 has anapex seal 52 extending from one end face 26 to the other and protrudingradially from the peripheral face 28. Each apex seal 52 is biasedradially outwardly against the peripheral wall 18 through a respectivespring. An end seal 54 engages each end of each apex seal 52, and isbiased against the respective end wall 14 through a suitable spring.Each end face 26 of the rotor 24 has at least one arc-shaped face seal60 running from each apex portion 30 to each adjacent apex portion 30,adjacent to but inwardly of the rotor periphery throughout its length. Aspring urges each face seal 60 axially outwardly so that the face seal60 projects axially away from the adjacent rotor end face 26 intosealing engagement with the adjacent end wall 14 of the cavity. Eachface seal 60 is in sealing engagement with the end seal 54 adjacent eachend thereof.

Although not shown, each rotor 24 is journaled on an eccentric portionof a shaft and includes a phasing gear co-axial with the rotor axis,which is meshed with a fixed stator phasing gear secured to the outerbody co-axially with the shaft. In a particular embodiment where theengine 10 includes multiple rotors 24 and cavities 20, each rotor 24 maybe journaled on a respective eccentric portion of a same shaft. Theshaft rotates each rotor 24 and the meshed gears guide the rotor 24 toperform orbital revolutions within the respective rotor cavity 20. Theshaft rotates three times for each complete rotation of the rotor 24 asit moves around the rotor cavity 20. Oil seals are provided around thephasing gear to prevent leakage flow of lubricating oil radiallyoutwardly thereof between the respective rotor end face 26 and outerbody end wall 14.

For each rotor cavity 20, at least one inlet port 44 is defined throughone of the end walls 14 or the peripheral wall 18 for admitting air(atmospheric or compressed) into one of the working chambers 32, and atleast one exhaust port 46 is defined through one of the end walls 14 orthe peripheral wall 18 for discharge of the exhaust gases from thecombustion chambers 32. The inlet and exhaust ports 44, 46 arepositioned relative to each other and relative to the ignition memberand fuel injectors (further described below) such that during eachrotation of the rotor 24, each chamber 32 moves around the cavity 20with a variable volume to undergo the four phases of intake,compression, expansion and exhaust, these phases being similar to thestrokes in a reciprocating-type internal combustion engine having afour-stroke cycle.

In a particular embodiment, the inlet and exhaust ports 44, 46 arearranged such that the rotary engine 10 operates under the principle ofthe Miller or Atkinson cycle, with its volumetric compression ratiolower than its volumetric expansion ratio. In another embodiment, theinlet and exhaust ports 44, 46 are arranged such that the volumetriccompression and expansion ratios are equal or similar to one another.

The engine 10 includes a pilot subchamber 72 for each rotor cavity 20,defined in the outer body 12, for pilot fuel injection and ignition. Inthe embodiment shown, the pilot subchamber 72 is provided in an insert34 received in a corresponding hole 36 defined through the peripheralwall 18 of the outer body 12. The insert 34 is retained to theperipheral wall 18 using any adequate type of connection, including, butnot limited to, fasteners, welding, brazing, retention through a coveroverlapping the insert 34 and connected to the peripheral wall 18, etc.In another embodiment, the pilot subchamber 72 is directly defined inthe peripheral wall 18.

In the embodiment shown, the insert body 34 has the entire pilotsubchamber 72 defined therein, shown here with a circular cross-section.Other geometries are also possible, including but not limited tocylindrical, conical, frustoconical, wedge-shaped profiles, etc. Theinsert 34 includes at least one outlet opening 74 defined therein forcommunication with the cavity 20, and the subchamber 72 has a shapeforming a reduced cross-section adjacent the opening(s) 74, such thatthe opening(s) 74 define a restriction to the flow between thesubchamber 72 and the cavity 20. The opening(s) 74 may have variousshapes and/or be defined by a pattern of multiple holes.

The particular insert 34 shown is provided only as an example, and it isunderstood that other geometries and/or positions within the peripheralwall 18 are possible for the insert 34. In a particular embodiment, theinsert 34 is made of a material having a greater high temperatureproperties and/or lower thermal conductivity than that of the peripheralwall 18, which may be for example made of aluminum. In one embodiment,the insert 34 is made of a nickel or cobalt based super alloy.Alternately, as mentioned above, the insert 34 may be omitted and thepilot subchamber 72 be directly defined in the peripheral wall 18 if theperipheral wall 18 is made of a material having sufficient heatresistance and adequate high temperature properties to resist the hightemperatures within the subchamber 72.

The peripheral wall 18 of each rotor cavity 20 has a main injectorelongated hole 40 defined therethrough, in communication with the rotorcavity 20 and spaced apart from the pilot subchamber 72. A main fuelinjector 42 is received and retained within this corresponding hole 40,with the tip of the main injector 42 communicating with the cavity 20 ata point spaced apart from the pilot subchamber 72. The main injector 42is located rearwardly of the pilot subchamber 72 with respect to thedirection R of the rotor rotation and revolution, and is angled todirect fuel forwardly into each of the rotating chambers 32 sequentiallywith a tip hole pattern designed for an adequate spray.

The peripheral wall 18 of each rotor cavity 20 also has a pilot injectorelongated hole 76 defined therethrough in communication with thesubchamber 72. A pilot fuel injector 78 is received and retained withinthe corresponding hole 76, with the tip of the pilot injector 78 beingin communication with the subchamber 72, for example by terminating in acorresponding opening defined in the insert 34 between the subchamber 72and the pilot injector hole 76. It can be seen that the main injector 42and pilot injector 78 are spaced apart from one another.

The pilot injector 78 and main injector 42 of each rotor cavity 20inject fuel, which in a particular embodiment is heavy fuel e.g. diesel,kerosene (jet fuel), equivalent biofuel, etc. into the chambers 32.Alternately, the fuel may be any other adequate type of fuel suitablefor injection as described, including non-heavy fuel such as for examplegasoline or liquid hydrogen fuel. In a particular embodiment, at least0.5% and up to 20% of the fuel is injected through the pilot injector78, and the remainder is injected through the main injector 42. Inanother particular embodiment, at most 10% of the fuel is injectedthrough the pilot injector 78. In another particular embodiment, at most5% of the fuel is injected through the pilot injector 78. The maininjector 42 injects the fuel such that each rotating chamber 32 when inthe combustion phase contains a lean mixture of air and fuel.

The peripheral wall 18 of each rotor cavity 20 and, in the embodimentshown, the insert body 34 have an ignition element elongated hole 82defined therein in communication with the subchamber 72. An igniter orignition element 84 is received and retained within the correspondinghole 82 and positioned to ignite fuel within the subchamber 72, e.g.with the tip of the ignition element 84 being received in the subchamber72. In the embodiment shown, the ignition element 84 is a glow plug.Other configurations are also possible, including for example having theignition element 84 completely received within the insert 34, and/orignition element(s) 84 of any other adequate type, including but notlimited to plasma ignition, laser ignition, spark plug, microwave, othertypes of ignition elements, etc.

Referring to FIG. 2, in a particular embodiment, the main fuelinjector(s) 42 and the pilot fuel injector(s) 78 of the engine 10 are influid communication with a same common rail 100. The common rail 100 hasan the inlet 108 in fluid communication with a pump system 106. In theembodiment shown, the pump system 106 includes a low pressure pump 110located in or in fluid communication with a fuel source or fuel tank112, and a high pressure pump 114 receiving the fuel from the lowpressure pump 110 and feeding it to the inlet 108 of the common rail100.

The common rail 100 has an outlet 116 in selective fluid communication,directly or indirectly, with the fuel tank 112 such as to return anexcess of fuel thereto. In the embodiment shown, a metering or pressureregulating valve 118 is provided at the outlet 116 to regulate the flowof fuel therethrough. A pressure regulating mechanism regulates the fuelpressure in the common rail and may be provided in the pump system 106(e.g. metering unit) and/or by the valve 118.

In the embodiment shown, an engine control unit 120 controls the pilotand main fuel injection through control of the high pressure pump 114(e.g. actuation, fuel pressure and/or fuel flow), the valve 118 (e.g.position) and the fuel injectors 42, 78 (e.g. actuation of electronicvalves controlling the injection pulses).

In a particular embodiment, the engine 10 has a single moveable body 24,24′, with a single main injector 42 and a single pilot injector 78 influid communication with the common rail 100. In another embodiment, theengine 10 includes at least one additional moveable body 24, 24′, eachhaving an additional main injector 42 and an additional pilot injector78 (one being shown in dotted lines in FIG. 2) also in fluidcommunication with the same common rail 100.

In use, the fuel is combusted by pressurizing the fuel in the commonrail 100, feeding the pilot injector(s) 78 with the common rail 100 toinject the fuel in the pilot subchamber(s) 72 where it is ignited andcirculated into a respective combustion chamber 32, and feeding the maininjector(s) 42 with the common rail 100 to inject the fuel into thecombustion chamber 32. The pilot and main injections are thus performedspaced apart from one another.

In a particular embodiment, both the main and pilot injectors 42, 78inject the fuel using the pressure provided in the common rail 100, e.g.without the use of pressure intensification mechanisms. In a particularembodiment, a difference in fuel volume between the pilot and maininjections may be provided by tuning the duration and/or number ofinjection pulses and/or by using a pilot injector 78 having a smalleropen area A_(p), as defined by the tip openings through which the fuelis injected, than the open area A_(m) of the main injector 42 (see FIG.1).

In the embodiment shown in FIG. 3, the engine 10 includes multiplemoveable bodies 24, 24′, and as such a plurality of main fuel injectors42 and pilot fuel injectors 78 (three in the embodiment shown). All themain fuel injectors 42 are in fluid communication with a same commonprimary fuel conduit 202, while all the pilot fuel injectors 45 are influid communication with a same common secondary fuel conduit 204. Aprimary pressure regulating mechanism regulates the fuel pressure in theprimary fuel conduit 202 while a secondary pressure regulating mechanismregulates a fuel pressure in the secondary conduit 204. The primary andsecondary pressure regulating mechanisms are settable at differentpressure values from one another such that the primary and secondaryfuel conduits 202, 204 can provide fuel at different pressures.

In the particular embodiment shown, the primary and secondary conduits202, 204 are separate chambers defined side by side in a same commonrail 200. The inlet 208 of the common rail 200 and of the primary fuelconduit 202 is in fluid communication with a pump system 206 (e.g.single or multiple pump arrangement) providing for the primary pressureregulating mechanism (e.g. through a metering unit), by regulating thefuel flow from the pump system 206 to the primary conduit 202.

The primary and secondary conduits 202, 204 are in selective fluidcommunication with each other through a metering or pressure regulatingvalve 222 which is also in selective fluid communication with the fueltank 112 such as to return an excess of fuel thereto. In a particularembodiment, the valve 222 is a metering valve. The secondary conduit 204has an outlet 216 (also corresponding to the outlet of the common rail200) in selective fluid communication, directly or indirectly, with thefuel tank 112 such as to return an excess of fuel thereto. In theembodiment shown, a second metering or pressure regulating valve 218 isprovided at the outlet of the secondary conduit to regulate the flow offuel therethrough. As such, in the embodiment shown, the pressureregulating mechanism of the secondary conduit 204 may be provided by theinlet valve 222 and/or the outlet valve 218.

In the embodiment shown, the engine control unit 120 controls the pilotand main fuel injection through control of the pump system 206 (e.g.actuation, fuel pressure and/or fuel flow), the valves 218, 222 (e.g.position) and the fuel injectors 42, 78 (e.g. actuation of electronicvalves controlling the injection pulses).

In a particular embodiment, the different pressures of the main andpilot injection allows for main and pilot injectors 42, 78 having asimilar size and configuration to be used while still obtaining asmaller fuel volume in the pilot injection than in the main injection.Alternately, as above, the pilot injector 78 may have a smaller openarea, as defined by the tip openings through which the fuel is injected,than that of the main injector 42.

In use, the fuel is combusted by pressurizing the fuel in the primaryand secondary conduits 202, 204 to obtain different fuel pressures,feeding the pilot injectors 78 with the primary conduit 202 to injectfuel in the respective pilot subchamber 72 where it is ignited andcirculated into a respective combustion chamber 32, and feeding the maininjectors 42 with the secondary conduit 204 to inject fuel into thecombustion chamber 32.

Alternately, the primary conduit 202 may be connected to the maininjectors 42 and the secondary conduit 204 may be connected to the pilotinjectors 78.

The embodiment shown in FIG. 4 is similar to the embodiment shown inFIG. 3. However, in this embodiment, the primary and secondary conduits302, 304 are respectively defined by separate common rails. A first pumpsystem 306 (e.g. single or multiple pump arrangement) is in fluidcommunication with the fuel source and with the inlet 308 of the primaryconduit. A second pump system 307 (e.g. single or multiple pumparrangement) is in fluid communication with the fuel tank 112 and withthe inlet 309 of the secondary conduit 304.

Each conduit 302, 304 has an outlet 315, 316 in selective fluidcommunication, directly or indirectly, with the fuel tank 112 such as toreturn an excess of fuel thereto. In the embodiment shown, a metering orpressure regulating valve 322, 318 is provided at the outlet 315, 316 ofeach conduit 302, 304 to regulate the flow of fuel therethrough. Theprimary pressure regulating mechanism may thus provided in the firstpump system 306 (e.g. metering unit) and/or by the first valve 322,while the secondary pressure regulating mechanism may be provided in thesecond pump system 307 (e.g. metering unit) and/or by the second valve318.

In the embodiment shown, the engine control unit 120 controls the pilotand main fuel injection through control of the pump systems 306, 307(e.g. actuation, fuel pressure and/or fuel flow), the valves 318, 322(e.g. position) and the fuel injectors 42, 78 (e.g. actuation ofelectronic valves controlling the injection pulses). Alternately, thepump system and valve associated with each of the conduits may becontrolled by a different engine control unit.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the invention disclosed.Modifications which fall within the scope of the present invention willbe apparent to those skilled in the art, in light of a review of thisdisclosure, and such modifications are intended to fall within theappended claims.

The invention claimed is:
 1. A rotary internal combustion enginecomprising: a first common rail having a first metering or pressureregulating valve in fluid communication therewith; a second common railhaving a second metering or pressure regulating valve in fluidcommunication therewith, the first and second metering or pressureregulating valves being settable at different pressure values from oneanother; and at least two rotors each sealingly and rotationallyreceived within a respective cavity to define at least one combustionchamber of variable volume; and for each of the rotors, a first fuelinjector in fluid communication with the first common rail and a secondfuel injector in fluid communication with the second common rail.
 2. Theengine as defined in claim 1, further comprising a first pump in fluidcommunication with a fuel source and with an inlet of the first commonrail and a second pump in fluid communication with the fuel source andwith an inlet of the second common rail.
 3. The engine as defined inclaim 2, wherein the first metering or pressure regulating valve isprovided at an outlet of the first common rail, the second metering orpressure regulating valve is provided at an outlet of the second commonrail, and the outlets of the first and second metering or pressureregulating valves are in fluid communication with the fuel source. 4.The engine as defined in claim 2, wherein the first and second pumps andthe first and second metering or pressure regulating valves are actuableby an engine control unit.
 5. The engine as defined in claim 1, whereinthe first and second fuel injectors have a size and configurationsimilar to each other.
 6. The engine as defined in claim 1, wherein thefirst and second fuel injectors have tip openings through which the fuelis injected, and an open area defined by the tip openings of the secondfuel injector is smaller than that defined by the tip openings of thefirst fuel injector.
 7. The engine as defined in claim 1, wherein thefirst metering or pressure regulating valve is provided at an outlet ofthe first common rail and the second metering or pressure regulatingvalve is provided at an outlet of the second common rail.
 8. The engineas defined in claim 1, wherein each respective cavity is defined by twoaxially spaced apart end walls and a peripheral wall extending betweenthe end walls, and each of the at least two rotors is rotatable withinthe respective cavity in sealing engagement with the peripheral and endwalls.
 9. The engine as defined in claim 8, wherein each of the at leasttwo rotors has three circumferentially spaced apex portions and therespective cavity defines an epitrochoid shape with two lobes, the atleast one combustion chamber include three rotating chambers of variablevolume, the at least two rotors being engaged to an eccentric portion ofa shaft to rotate and perform orbital revolutions within the respectivecavity with each of the apex portions remaining in sealing engagementwith the peripheral wall and separating the chambers.
 10. A rotaryinternal combustion engine comprising: a first common rail having afirst metering or pressure regulating valve in fluid communicationtherewith; a second common rail having a second metering or pressureregulating valve in fluid communication therewith, the first and secondmetering or pressure regulating valves being settable at differentpressure values from one another; an outer body having at least tworotor cavities each defined by two axially spaced apart end walls and aperipheral wall extending between the end walls; a rotor received ineach of the at least two rotor cavities, each rotor being rotatablewithin the rotor cavity in sealing engagement with the peripheral andend walls and defining at least one chamber of variable volume in therotor cavity; for each of the rotor cavities, a first fuel injector influid communication with the first common rail; and for each of therotor cavities, a second fuel injector in fluid communication with thesecond common rail.
 11. The engine as defined in claim 10, wherein eachof the rotor cavities defines an epitrochoid shape with two lobes, andeach rotor has three circumferentially spaced apex portions, and the atleast one combustion chamber include three rotating chambers of variablevolume, the rotor being engaged to an eccentric portion of a shaft torotate and perform orbital revolutions within the rotor cavity with eachof the apex portions remaining in sealing engagement with the peripheralwall and separating the chambers.
 12. The engine as defined in claim 10,further comprising a first pump in fluid communication with a fuelsource and with an inlet of the first common rail and a second pump influid communication with the fuel source and with an inlet of the secondcommon rail.
 13. The engine as defined in claim 12, wherein the firstmetering or pressure regulating valve is provided at an outlet of thefirst common rail, the second metering or pressure regulating valve isprovided at an outlet of the second common rail, and the outlets of thefirst and second metering or pressure regulating valves are in fluidcommunication with the fuel source.
 14. The engine as defined in claim10, wherein the first and second fuel injectors have a size andconfiguration similar to each other.
 15. The engine as defined in claim10, wherein the first and second fuel injectors have tip openingsthrough which the fuel is injected, and an open area defined by the tipopenings of the second fuel injector is smaller than that defined by thetip openings of the first fuel injector.
 16. The engine as defined inclaim 10, wherein the first metering or pressure regulating valve isprovided at an outlet of the first common rail.
 17. The engine asdefined in claim 10, wherein the second metering or pressure regulatingvalve is provided at an outlet of the second common rail.
 18. A methodof feeding fuel in an internal combustion engine having at least tworotors each defining at least one combustion chamber, the methodcomprising: pressurizing the fuel in a first common rail at a firstpressure; pressurizing the fuel in a second common rail separate fromthe first common rail at a second pressure different from the firstpressure; and for each of the rotors of the engine: feeding a respectivefirst injector with fuel at the first pressure from the first commonrail; and feeding a respective second injector with fuel at the secondpressure from the second common rail.
 19. The method as defined in claim18, wherein the fuel is heavy fuel.
 20. The method as defined in claim18, wherein pressurizing the fuel in the first common rail andpressurizing the fuel in the second common rail includes regulating thefirst and second pressures with at least one engine control unit.